Monthly Archives: May 2015

Mantis shrimp look fragile but pack a powerful punch

Published May 25, 2016 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2016 Susan Scott

mantis

Some years ago, I sailed to Australia’s Lizard Island, where researchers kindly allowed me to wander around their laboratory on my own. One day I found, kind of sitting up in a white cup, a 4-inch-long creature in a clown suit.

I had no idea what studies the biologists were conducting on the stunning animal, but whatever they were it deserved the attention.

I was looking at a peacock mantis shrimp.

The peacock mantis shrimp is the most colorful of the 400 or so mantis shrimp species found in the warm waters of the Indian and Pacific oceans, but researchers are interested in them all. The eyes, claws and intelligence of these crustaceans are so extraordinary that discoveries about them have made national news.

The mantis shrimp’s shape resembles a shrimp, and the folded front limbs look like those of the praying mantis.

Mantis shrimps are a type — and force — all their own. (Distantly related to shrimp, lobsters and crabs, they occupy their own order as stomatopods.)

The force comes in the form of two hinged claws, the front ends folded under the second segments like a praying mantis. Those tucked-under parts are either knives or clubs, depending on species.

When a mantis shrimp finds a fish or crab, it shoots out the cocked claws at bullet speed, and depending on weaponry, impales the fish or wallops the crab. Check out the video of this behavior at bit.ly/1RY3CO3.

Mantis shrimp zero in on prey with the most sophisticated vision of all animals, including us. To scan the surroundings, the two stalked eyes can independently swivel vertically and horizontally. Each eye has exceptional depth perception, plus 16 visual pigments (people have four) to see far beyond the human range, including ultraviolet and polarized light.

Besides toting lethal weapons and having nearly X-ray vision, mantis shrimp are also the Einsteins of crustaceans. In one study, researchers gave a peacock mantis shrimp two hollow plastic tubes of different colors and patterns with a plate of opaque glass covering the open end. One tube contained food.

The mantis shrimp had to break the glass, a natural behavior in this clubbing species, to get into the tube. The creature quickly learned which tube color and pattern contained food, consistently breaking open the right one and ignoring the other.

Some mantis shrimp live 20 years and mate for life.

Hawaii hosts 17 species (alas, no peacock). If you find one, admire it but don’t touch. Punching mantis shrimps can break aquarium glass and the stabbers’ nickname is “thumb splitter.”


Marine biologist Susan Scott writes the newspaper column, “Ocean
Watch”, for the Honolulu Star-Advertiser, www.staradvertiser.com

©2015 Susan Scott

 

Ribbon worm’s star turn shows its dynamic range

Published May 18, 2015 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2015 Susan Scott

A friend sent the link to the video above with a note: “This worm is trending on YouTube. Have you seen it?”

I have now, many times, because unlike unenlightened viewers who wrote “Gross!” “Creepy!” “Disgusting!” and worse, I loved it. This is why so many of us are crazy about marine biology. The animals are out of this world.

The video shows a ribbon worm in hunting mode.

Ribbon worms are carnivores that eat shrimp, crabs, clams and segmented worms (another kind of worm). Most are flat but thicker.

The video came from Thailand but ribbon worms are widespread. Researchers have identified about 1,200 species. Hawaii hosts 10.

Most are about 8 inches long, but some are so small they’re barely visible. At the other end of the spectrum is the bootlace worm, reaching the extraordinary length of 100 feet.

I imagined that a worm so outlandishly long would be rare. But no. Living in a twisted heap under rocks and in sand and mud, the bootlace worm is common along the shorelines of the British Isles.

Besides the huge range of sizes, ribbon worms also come in various colors and patterns. But all species of ribbon worms have one famous feature in common: a long flexible snout called a proboscis.

The snout isn’t a mouth, nor is it even connected to the digestive tract. A ribbon worm’s proboscis is an eye-popping tool that it uses to catch prey.

Inside the snout is a fluid-filled cavity holding a coiled, hollow, branched tube with an opening to the outside at the tip. Lining the inside of the convoluted tube is a sticky toxin. Some species have a barb at the far end of their tube to deliver their toxin by stabbing.

When the worm finds something live to eat, it contracts muscles around the snout, causing the tube to shoot out the hole inside out. (Picture blowing a latex glove inside out.) The tube’s gluey inverted branches wrap around the prey, and the toxin paralyzes it. In species with a barb, the worm injects its toxin.

Once the prey is immobile, the worm sucks the animal into its mouth, located on the underside.

As if that’s not enough coolness in one creature, when it comes to reproducing, ribbon worms take no chances. The worms are either male or female and can reproduce with sperm and eggs. But this is no hit-or-miss spewing in the water as is common in other marine animals. In some species, when the female finds a male, she builds a cocoon around herself and her mate. Thus enclosed, the sperm hits right on target.

Other species can clone themselves, handy when a member of the opposite sex isn’t available. The worm’s body breaks at preformed places that look like rings, and each piece grows into a complete worm.

I watched this 29-second video over and over — on mute because I disliked the creepy sound effects.

Ribbon worms are stunning designs of nature. I hope that someday we will live in a world where, about such extraordinary animals, people will write, “Fantastic!” “Brilliant!” “Excellent!”

And play Elvis Presley’s “Stuck on You.”


Marine biologist Susan Scott writes the newspaper column, “Ocean
Watch”, for the Honolulu Star-Advertiser, www.staradvertiser.com

©2015 Susan Scott

 

 

 

 

Messages arrive on the tide to please a seagoing scribe

That’s a moray. ©2015 Susan Scott

That’s a moray. ©2015 Susan Scott

Thank you, thoughtful readers, for sharing marine reports that brighten my day. In this era of so much bad news about the world’s oceans, it’s a relief to read items about them that make me smile.

Such as Obeka’s release. Obeka is the giant Pacific octopus I fell in love with while visiting the Fiero Marine Center in Port Angeles, Wash. On April 26, workers there took Obeka back to her ocean home.

Obeka

When she came to live at the center, Obeka weighed only 3 ounces. Upon returning to the sea 14 months later, the octopus weighed 35 pounds. Hopefully Obeka will find a mate, lay her 68,000 eggs and tend them until they hatch about nine months later.

Obeka will die soon after her eggs hatch, as all octopuses do, but I don’t feel sad. The creature served as a stellar ambassador for her species and will leave behind the ultimate gift: offspring.

Besides being impressed by octopuses, I’m also obsessed with sea snakes. A friend who knows of my snaky passion sent me a study regarding the bar-bellied sea snake found near the coastline of Western Australia.

sea krait

Sea snakes don’t have many predators, but tiger sharks are one of them. Researchers discovered that at high tide, when the water is deep enough for the sharks to swim near shore, the snakes hang out in sea grass beds where their main source of food, fish, is scarce. When the tide goes out, though, so do the sharks, and the snakes resume their usual hunting over sand flats.

But the study doesn’t just show that sea snakes are smart enough to avoid predators — most prey animals are. It’s also a heads-up to biologists. When studying habitat and foraging behaviors of the bar-bellied sea snake, researchers need to note the state of the tides.

Bar-bellied sea snakes are the longest of all sea snakes, growing to 6 feet. I’ve not seen one. I live in hope.

Another reader sent a National Geographic link about by-the-wind sailors.

While approaching Australia’s east coast last fall, I sailed through massive numbers of these jelly creatures for 24 hours. The ones I saw peppered the water’s surface far and wide. But when the wind and currents are just right, or just wrong if you’re a by-the-wind sailor, the creatures run aground. Check out these amazing photos of millions of these jellies shipwrecked last month on West Coast beaches: bit.ly/1GVK0UH.

Scooped at sea_small

Finally, as a reminder that I shouldn’t take the negative news crowding my inbox too seriously, I’ll keep in mind last week’s message from a snorkeling buddy:

“When you’re down by the sea,

And an eel bites your knee,

That’s a moray.”

Thanks everyone for messages that make me smile.


Marine biologist Susan Scott writes the newspaper column, “Ocean
Watch”, for the Honolulu Star-Advertiser, www.staradvertiser.com

©2015 Susan Scott

 

Nature’s mightiest material gives opihi teeth their bite

Published May 4, 2015 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2015 Susan Scott
Black-foot opihi are also known as limpets. ©2015 Susan Scott

Black-foot opihi are also known as limpets.
©2015 Susan Scott

Until recently, researchers thought spider silk was nature’s strongest material. Now the title goes to limpet teeth.

Using high-tech microscopy, engineers at the University of Portsmouth, England, studied the structure of limpet teeth and discovered they consist of fibers combining an iron-based mineral with a protein.

In testing how much force those tightly packed fibers could withstand before breaking (engineers do the darndest things), the researchers got a surprise. The teeth equaled the strength of man-made carbon fiber but were more flexible. To picture how extraordinary this is, imagine 3,300 pounds of rice dangling from one string of spaghetti.

The exciting discovery has the potential to shape the future building materials of airplanes, cars, boats and even dental fillings.

Who knew that limpets, called opihi in Hawaii, even had teeth? They do. Dozens of tiny teeth line an opihi’s tongue, a muscular structure rolled up inside the snail’s body. When it’s time to eat, the limpet unrolls its prickly tongue, strolls around its rocky neighborhood and scrapes up algae.

Limpets also chew rocks. In the proc­ess of cropping algae, the tough teeth break off pieces of rock. The creature’s digestive system absorbs the algae but hardens the rock pieces and expels them in fecal pellets resembling tiny cakes of concrete.

Rock eating is also handy for excavating homes on wave-washed shorelines. After foraging, each opihi returns to its “home scar,” a depression it has dug in a rock.

Hawaii hosts four opihi species found only in the isles, ranging from 2 inches in diameter to 4. Another smaller limpet, about three-quarters of an inch in diameter, called the false opihi, belongs to another family. Hawaiians named it opihi awa, meaning bitter opihi, and did not eat it.

Lots of people, however, ate the tasty others until they became scarce in the main islands.

Because so many people have lost their lives picking opihi on rocky shores pounded by big surf, opihi are considered one of the most dangerous marine animals in Hawaii waters. One historian wrote that opihi gathering was so dangerous, it was known in old Hawaii as the “fish of death.”

To conserve this popular snail snack, and give opihi a chance to mow down algae growth, state laws regulate opihi picking. To take one, the shell diameter must be at least 11⁄4 inches.

If you’re eating one of the cap-shaped snails, though, don’t bother looking for its teeth. At less than a millimeter long, they’re too small for the human eye to see.


Marine biologist Susan Scott writes the newspaper column, “Ocean
Watch”, for the Honolulu Star-Advertiser, www.staradvertiser.com

©2015 Susan Scott